Left Ventricular Pressure Overload Research Articles

P195 CARDIOVASCULAR OUTCOMES IN PATIENTS WITH AORTIC STENOSIS AND HYPERTENSION UNDERGOING AORTIC VALVE REPLACEMENT

Background and Objective: Aortic valve stenosis (AS) is most common valvular heart disease and in its severe form requires aortic valve replacement (AVR). The prevalence of both AS and arterial hypertension (HTN) increases with age and the conditions therefore often co-exist. Co-existence of AS and HTN is associated with higher global left ventricular (LV) pressure overload, more abnormal LV geometry and function, and more adverse cardiovascular outcome. Management of HTN in AS has historically been associated with prudence and concerns, mainly related to drug-induced potential adverse consequences. We evaluated the cardiovascular outcomes of patients with AS and HTN undergoing to AVR Methods: A retrospective cohort study where all the patients who underwent AVR between 2019- 2024, in a 4-level center in Bogotá, Colombia. A descriptive analysis was performed. Continuous variables were expressed as mean or median with their respective measure of dispersion, standard deviation or interquartile range (ICR), the categorical variables were expressed in proportions and absolute numbers. Results: We analyzed 1043 Patients with moderate/severe AS undergoing AVR, 64.3% (671 with HTN), median age for all of 69.8 years ICR (61.7-77.4) Hypertensive patient being older (72 years p<0.0001). In the HTN group 57.8% were men, and more frequently they had diabetes and dyslipidemia comorbidities (p<0.001) as well as greater baseline renal involvement (p<0.001) comparatively with NO-HTN. In addition, hypertensive patient had better LVEF and were treated with ARA II/IECA (55,6% vs 19.4% p<0.001), beta blockers (60.4% vs 47.3% p< 0.001) and anti-calcium medication (13,1% vs 19,5% p<0.001).Table 1. Cardiovascular outcomes showed greater tendency towards worsening of renal function. There were no statistically significant differences in mortality. Conclusions: AVR is presented as a safe procedure in patients with AS and HTN in developing countries. The institutional results show a safe technique, associated with low mortality rates. Hypertensive patients had more acute kidney injury in the post-surgical period, which leads us to propose kidney protection strategies in this group.

Abstract Tu094: p53 Regulates the Extent of Fibroblast Proliferation and Fibrosis in Left Ventricle Pressure Overload

Background: Cardiomyopathy is characterized by the pathological accumulation of resident cardiac fibroblasts that deposit ECM (extracellular matrix) and generate a fibrotic scar. However, the mechanisms that control the timing and extent of cardiac fibroblast proliferation and ECM production are not known, hampering the development of antifibrotic strategies to prevent heart failure. Methods: We used the Tcf21 (transcription factor 21) MerCreMer mouse line for fibroblast-specific lineage tracing and p53 (tumor protein p53) gene deletion. We characterized cardiac physiology and used single-cell RNA-sequencing and in vitro studies to investigate the p53-dependent mechanisms regulating cardiac fibroblast cell cycle and fibrosis in left ventricular pressure overload induced by transaortic constriction. Results: Cardiac fibroblast proliferation occurs primarily between days 7 and 14 following transaortic constriction in mice, correlating with alterations in p53-dependent gene expression. p53 deletion in fibroblasts led to a striking accumulation of Tcf21- lineage cardiac fibroblasts within the normal proliferative window and precipitated a robust fibrotic response to left ventricular pressure overload. However, excessive interstitial and perivascular fibrosis does not develop until after cardiac fibroblasts exit the cell cycle. Single-cell RNA sequencing revealed p53 null fibroblasts unexpectedly express lower levels of genes encoding important ECM proteins while they exhibit an inappropriately proliferative phenotype. in vitro studies establish a role for p53 in suppressing the proliferative fibroblast phenotype, which facilitates the expression and secretion of ECM proteins. Importantly, Cdkn2a (cyclin-dependent kinase inhibitor 2a) expression and the p16Ink4a-retinoblastoma cell cycle control pathway is induced in p53 null cardiac fibroblasts, which may eventually contribute to cell cycle exit and fulminant scar formation. Conclusions: This study reveals a mechanism regulating cardiac fibroblast accumulation and ECM secretion, orchestrated in part by p53-dependent cell cycle control that governs the timing and extent of fibrosis in left ventricular pressure overload.

Soft robotic platform for progressive and reversible aortic constriction in a small-animal model.

Our understanding of cardiac remodeling processes due to left ventricular pressure overload derives largely from animal models of aortic banding. However, these studies fail to enable control over both disease progression and reversal, hindering their clinical relevance. Here, we describe a method for progressive and reversible aortic banding based on an implantable expandable actuator that can be finely tuned to modulate aortic banding and debanding in a rat model. Through catheterization, imaging, and histologic studies, we demonstrate that our platform can recapitulate the hemodynamic and structural changes associated with pressure overload in a controllable manner. We leveraged soft robotics to enable noninvasive aortic debanding, demonstrating that these changes can be partly reversed because of cessation of the biomechanical stimulus. By recapitulating longitudinal disease progression and reversibility, this animal model could elucidate fundamental mechanisms of cardiac remodeling and optimize timing of intervention for pressure overload.

Right ventricular pacing-evoked left ventricular dysfunction is exaggerated by sustained left ventricular pressure overload in a rat model

Abstract Introduction A growing body of evidence suggests that in the presence of left bundle branch block-induced electromechanical dyssynchrony, the function of the left ventricle (LV) becomes extremely sensitive to arterial afterload. However, data is scarce whether right ventricular pacing (RVP) also sensitizes the LV to alterations in afterload. Purpose Hence, in the present translational study we aimed to characterize the acute effect of RVP on LV hemodynamics under standard laboratory conditions using a rat model of chronic LV pressure overload (PO). Methods Transverse aortic constriction (TAC group) was carried out in male Wistar rats to evoke sustained LV PO for six weeks. Age- and sex-matched sham-operated animals served as controls (Sham group). LV hemodynamics was assessed in anesthetized rats by pressure-volume analysis using a pressure-conductance micro-catheter (SPR-838) introduced to the LV via the right carotid artery. To evoke RVP, the right jugular vein was cannulated and an ultra-miniature octopolar electrophysiology catheter (EPR-800) was placed into the right ventricle. Pressure-volume loops were registered in the TAC and the Sham groups during intrinsic narrow QRS rhythm (termed as TAC-Vsense and Sham-Vsense) as well as during RVP (termed as TAC-Vpace and Sham-Vpace). Results RVP was associated with impaired diastolic function (active relaxation time constant [τ]: 8.6±0.3 vs. 9.6±0.3ms, Sham-Vsense vs. Sham-Vpace and 8.0±0.3 vs. 9.6±0.4ms, TAC-Vsense vs. TAC-Vpace; P<0.001 for both comparisons) and decreased LV contractility (preload recruitable stroke work [PRSW]: 139±9 vs. 114±9mmHg, Sham-Vsense vs. Sham-Vpace and 255±23 vs. 169±17mmHg, TAC-Vsense vs. TAC-Vpace; P<0.001 for both comparisons) in both the TAC and the Sham groups. Nevertheless, the extent of RVP-evoked active relaxation prolongation (Δτ: 12±2 vs. 20±2%, Sham vs. TAC, P=0.005) and LV contractility reduction (ΔPRSW: -18±4 vs. -34±3%, Sham vs. TAC, P=0.007) was found to be more robust in rats with sustained LV PO compared to controls. Conclusion Our experimental results indicate that RVP-induced LV dysfunction is exaggerated in case of sustained LV PO.

Neutrophils orchestrate early cardiac remodeling after cardiac pressure overload

Cardiac pressure overload is a chronic condition where the left ventricle undergoes pathological hypertrophy and fibrosis ultimately causing heart failure. Increased myocardial stretch in left ventricular pressure overload initiates activation of an inflammatory and fibrotic response within resident cells leading to infiltration of immune cells. Neutrophils and monocytes are among the first responders during cardiac injury. While the role of monocytes and macrophages in pressure overload has been somewhat elucidated by multiple groups, including our lab, the role of neutrophils in chronic cardiac injury such as pressure overload is still unclear. We hypothesized that, like acute ischemic injury, neutrophils infiltrate to the heart early in pressure overload and initiate an inflammatory cascade which worsens cardiac dysfunction after TAC and that depletion of neutrophils in the first week of TAC would improve cardiac function. Our published single cell RNAseq dataset of immune cells (CD45+) cells from sham and TAC heart at day (D) 7 shows a distinct clustering of neutrophils with S100a9 (34-fold) , S100a8 (31-fold) , Retnlg (9-fold) , Il1b (5-fold) , and Slpi (5-fold) as top 5 differentially expressed genes (DEGs). Geneset enrichment analysis of top 58 DEGs (≥1.5-folds), shows significant association with pathways such as innate immune system, neutrophil degranulation, and signaling by interleukins by Reactome 2022 pathway. Using a murine model of transaortic constriction (TAC) to induce left ventricular pressure overload, we evaluated cardiac neutrophil counts by flow cytometry over the first week of TAC at D 2, 4 and 7. We observed that neutrophils (CD45+Ly6G+CD11b+) numbers consistently increase until D4, with a 7-fold increase at D2 to a 17-fold increase at D4 before returning to sham levels by D7. Using antibody (Anti Gr-1, 4 ug/g) mediated depletion of neutrophils, we observed that neutrophil depletion showed a protective effect in females compared to isotype controls with decreased cardiac hypertrophy and improved ejection fraction; while in male mice no change was observed between isotype and antibody treated groups. In conclusion, our data show that neutrophils peak early in pressure overload and orchestrate early cardiac remodeling with a potential for a sexually dimorphic role. We acknowledge funding from National Institute of Health under the awards numbers HL155993 and HL160665. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Cardiac recovery from pressure overload is not altered by thyroid hormone status in old mice.

Thyroid hormones (THs) are known to have various effects on the cardiovascular system. However, the impact of TH levels on preexisting cardiac diseases is still unclear. Pressure overload due to arterial hypertension or aortic stenosis and aging are major risk factors for the development of structural and functional abnormalities and subsequent heart failure. Here, we assessed the sensitivity to altered TH levels in aged mice with maladaptive cardiac hypertrophy and cardiac dysfunction induced by transverse aortic constriction (TAC). Mice at the age of 12 months underwent TAC and received T4 or anti-thyroid medication in drinking water over the course of 4 weeks after induction of left ventricular pressure overload. T4 excess or deprivation in older mice had no or only very little impact on cardiac function (fractional shortening), cardiac remodeling (cardiac wall thickness, heart weight, cardiomyocyte size, apoptosis, and interstitial fibrosis), and mortality. This is surprising because T4 excess or deprivation had significantly changed the outcome after TAC in young 8-week-old mice. Comparing the gene expression of deiodinases (Dio) 2 and 3 and TH receptor alpha (TRα) 1 and the dominant-negative acting isoform TRα2 between young and aged mice revealed that aged mice exhibited a higher expression of TRα2 and Dio3, while expression of Dio2 was reduced compared with young mice. These changes in Dio2 and 3 expressions might lead to reduced TH availability in the hearts of 12-month-old mice accompanied by reduced TRα action due to higher TRα2. In summary, our study shows that low and high TH availability have little impact on cardiac function and remodeling in older mice with preexisting pressure-induced cardiac damage. This observation seems to be the result of an altered expression of deiodinases and TRα isoforms, thus suggesting that even though cardiovascular risk is increasing with age, the response to TH stress may be dampened in certain conditions.

Role of macrophages in regression of myocardial fibrosis following alleviation of left ventricular pressure overload.

Sustained hemodynamic pressure overload (PO) produced by murine transverse aortic constriction (TAC) causes myocardial fibrosis; removal of TAC (unTAC) returns left ventricle (LV) hemodynamic load to normal and results in significant, but incomplete regression of myocardial fibrosis. However, the cellular mechanisms that result in these outcomes have not been defined. The objective was to determine temporal changes in myocardial macrophage phenotype in TAC and unTAC and determine whether macrophage depletion alters collagen degradation after unTAC. Myocardial macrophage abundance and phenotype were assessed by immunohistochemistry, flow cytometry, and gene expression by RT-PCR in control (non-TAC), 2 wk, 4 wk TAC, and 2 wk, 4 wk, and 6 wk unTAC. Myocardial cytokine profiles and collagen-degrading enzymes were determined by immunoassay and immunoblots. Initial collagen degradation was detected with collagen-hybridizing peptide (CHP). At unTAC, macrophages were depleted with clodronate liposomes, and endpoints were measured at 2 wk unTAC. Macrophage number had a defined temporal pattern: increased in 2 wk and 4 wk TAC, followed by increases at 2 wk unTAC (over 4 wk TAC) that then decreased at 4 wk and 6 wk unTAC. At 2 wk unTAC, macrophage area was significantly increased and was regionally associated with CHP reactivity. Cytokine profiles in unTAC reflected a proinflammatory milieu versus the TAC-induced profibrotic milieu. Single-cell sequencing analysis of 2 wk TAC versus 2 and 6 wk unTAC revealed distinct macrophage gene expression profiles at each time point demonstrating unique macrophage populations in unTAC versus TAC myocardium. Clodronate liposome depletion at unTAC reduced CHP reactivity and decreased cathepsin K and proMMP2. We conclude that temporal changes in number and phenotype of macrophages play a critical role in both TAC-induced development and unTAC-mediated partial, but incomplete, regression of myocardial fibrosis.NEW & NOTEWORTHY Our novel findings highlight the dynamic changes in myocardial macrophage populations that occur in response to PO and after alleviation of PO. Our data demonstrated, for the first time, a potential benefit of macrophages in contributing to collagen degradation and the partial regression of interstitial fibrosis following normalization of hemodynamic load.

Hypoxia Attenuates Pressure Overload-Induced Heart Failure.

Alveolar hypoxia is protective in the context of cardiovascular and ischemic heart disease; however, the underlying mechanisms are incompletely understood. The present study sought to test the hypothesis that hypoxia is cardioprotective in left ventricular pressure overload (LVPO)-induced heart failure. We furthermore aimed to test that overlapping mechanisms promote cardiac recovery in heart failure patients following left ventricular assist device-mediated mechanical unloading and circulatory support. We established a novel murine model of combined chronic alveolar hypoxia and LVPO following transverse aortic constriction (HxTAC). The HxTAC model is resistant to cardiac hypertrophy and the development of heart failure. The cardioprotective mechanisms identified in our HxTAC model include increased activation of HIF (hypoxia-inducible factor)-1α-mediated angiogenesis, attenuated induction of genes associated with pathological remodeling, and preserved metabolic gene expression as identified by RNA sequencing. Furthermore, LVPO decreased Tbx5 and increased Hsd11b1 mRNA expression under normoxic conditions, which was attenuated under hypoxic conditions and may induce additional hypoxia-mediated cardioprotective effects. Analysis of samples from patients with advanced heart failure that demonstrated left ventricular assist device-mediated myocardial recovery revealed a similar expression pattern for TBX5 and HSD11B1 as observed in HxTAC hearts. Hypoxia attenuates LVPO-induced heart failure. Cardioprotective pathways identified in the HxTAC model might also contribute to cardiac recovery following left ventricular assist device support. These data highlight the potential of our novel HxTAC model to identify hypoxia-mediated cardioprotective mechanisms and therapeutic targets that attenuate LVPO-induced heart failure and mediate cardiac recovery following mechanical circulatory support.

Cardioprotection by the adiponectin receptor agonist ALY688 in a preclinical mouse model of heart failure with reduced ejection fraction (HFrEF)

AimsAdiponectin has been shown to mediate cardioprotective effects and levels are typically reduced in patients with cardiometabolic disease. Hence, there has been intense interest in developing adiponectin-based therapeutics. The aim of this translational research study was to examine the functional significance of targeting adiponectin signaling with the adiponectin receptor agonist ALY688 in a mouse model of heart failure with reduced ejection fraction (HFrEF), and the mechanisms of cardiac remodeling leading to cardioprotection. Methods and resultsWild-type mice were subjected to transverse aortic constriction (TAC) to induce left ventricular pressure overload (PO), or sham surgery, with or without daily subcutaneous ALY688-SR administration. Temporal analysis of cardiac function was conducted via weekly echocardiography for 5 weeks and we observed that ALY688 attenuated the PO-induced dysfunction. ALY688 also reduced cardiac hypertrophic remodeling, assessed via LV mass, heart weight to body weight ratio, cardiomyocyte cross sectional area, ANP and BNP levels. ALY688 also attenuated PO-induced changes in myosin light and heavy chain expression. Collagen content and myofibroblast profile indicated that fibrosis was attenuated by ALY688 with TIMP1 and scleraxis/periostin identified as potential mechanistic contributors. ALY688 reduced PO-induced elevation in circulating cytokines including IL-5, IL-13 and IL-17, and the chemoattractants MCP-1, MIP-1β, MIP-1alpha and MIP-3α. Assessment of myocardial transcript levels indicated that ALY688 suppressed PO-induced elevations in IL-6, TLR-4 and IL-1β, collectively indicating anti-inflammatory effects. Targeted metabolomic profiling indicated that ALY688 increased fatty acid mobilization and oxidation, increased betaine and putrescine plus decreased sphingomyelin and lysophospholipids, a profile indicative of improved insulin sensitivity. ConclusionThese results indicate that the adiponectin mimetic peptide ALY688 reduced PO-induced fibrosis, hypertrophy, inflammation and metabolic dysfunction and represents a promising therapeutic approach for treating HFrEF in a clinical setting.

T2D triggers distinct cardiac transcriptomic signatures in patients with severe aortic stenosis

Abstract Type 2 diabetes (T2D) is often associated to left ventricular (LV) pressure overload, as in aortic stenosis (AS). We reported, on DIAPASON cohort, that T2D increases adverse cardiac remodelling and dysfunction in patients with severe AS referred for aortic valve replacement. We aimed to study the underlying molecular mechanisms by a transcriptomic approach. We realised a transcriptomic analysis of LV cardiac biopsies obtained during aortic valve surgery from 17 T2D and 30 non-diabetic patients. Principal component analysis (PCA), on the 1029 significantly differentially expressed genes, shows a general segregation between T2D and non-diabetic patients. Functional enrichment maps reveal that 4 major biological processes are upregulated in T2D patients: regulation of inflammation, adaptation to cardiac hypertrophy, regulation of endothelial function/angiogenesis, and organisation of extracellular matrix. Decreased gene expression by T2D gathers 4 major biological processes: regulation of cardiac muscle contraction, mitochondrial organization, organization of mitochondrial respiratory chain and amino acid metabolism. After adjustment with other T2D comorbidities (age, sex, hypertension, BMI or the 4 combined), T2D effect remains mainly significant on the upregulated biological processes whereas the downregulation of amino acid metabolism, regulation of cardiac muscle contraction and mitochondrial transport processes seems to depend on hypertension and age. As an overlap was still present between T2D and non-diabetics transcriptomes in the PCA, we decided to use Factor Analysis of Mixed Data to identify potential subgroups of patients among the whole cohort. 84 patients have been clustered into 3 groups. Cluster 1 is associated with a patient profile without T2D and displaying a mild cardiac dysfunction, contrary to cluster 3 which includes mainly male T2D patients with a pronounced structural and functional cardiac alteration. Cluster 2 is only composed of female patients with higher BMI and leptin serum level, diastolic alteration and a moderately increased hypertrophy. Biological processes were differently affected between cluster 1 and cluster 2 or 3. Cluster 2 presents a decrease in gene expression involved in histone and protein demethylation. As for cluster 3, the expression of genes involved in immune response processes is increased while the one for the regulation of cardiac muscle organisation is decreased. To conclude, T2D is specifically associated with a reduction of gene expression involved in mitochondrial function, and an upregulation of angiogenesis, inflammation, and organisation of extracellular matrix. The unsupervised analysis revealed different clusters with specific gene expression and more specifically an association of female sex and metabolic syndrome with demethylation processes, and an association of T2D in men with inflammation and dysregulation of cardiac muscle contraction processes.Biological process in T2D patients

The type of suture material affects transverse aortic constriction-induced heart failure development in mice: a repeated measures correlation analysis.

Transverse-aortic constriction (TAC) operation is a widely used animal model to induce hypertrophy and heart failure through left-ventricular pressure overload. In mice, the cardiac response to TAC exhibits considerable variability influenced by factors such as strain, sub-strain, age, sex and vendor. To investigate the impact of suture material (silk versus prolene) and size (6-0 versus 7-0) on the TAC-induced phenotype, we performed surgeries on male C57BL6/N mice at 9 weeks of age defining the aortic constriction by a 27G needle, thereby employing most frequently used methodological settings. The mice were randomly assigned into four separate groups, 6-0 silk, 7-0 silk, 6-0 prolene and 7-0 prolene (10 mice per group). Echocardiography was conducted before TAC and every 4 weeks thereafter to monitor the development of heart failure. Repeated measures correlation analysis was employed to compare disease progression among the different groups. Our findings reveal a significant influence of the chosen suture material on TAC outcomes. Mice operated with prolene showed increased mortality, slower body weight gain, faster left-ventricular mass increase, and a faster decline in left-ventricular ejection fraction, fractional shortening and aortic pressure gradient compared to silk-operated mice. Moreover, despite non significant, using thinner suture threads (7-0) tended to result in a more severe phenotype compared to thicker threads (6-0) across all tested parameters. Collectively, our results highlight the importance of suture material selection in determining the cardiac phenotype induced by TAC and emphasize the need to consider this factor when comparing data across different research laboratories.

Abstract P2139: The Adiponectin Receptor Agonist ALY688 Prevents Pressure Overload-induced Cardiac Dysfunction And Adverse Cardiac Remodeling

Adiponectin has been shown to mediate multiple cardioprotective effects. Since the use of adiponectin protein as a practical therapeutic is associated with multiple challenges, we examined the functional significance of targeting adiponectin signaling with ALY688, a small peptide-based adiponectin mimetic, in a mouse model of cardiac dysfunction caused by left ventricular pressure overload (PO) induced by minimally invasive transverse aortic banding (MTAB). Following daily administration of ALY688 over 5 weeks after induction of PO, echocardiography showed that significantly attenuated PO-induced reduction in ejection fraction and other indices of cardiac function compared with vehicle. ALY688 also significantly reduced cardiac hypertrophic remodeling (heart weight-to-tibia length), cardiomyocyte cross sectional area, and myocardial and circulating levels of serum natriuretic peptide A. ALY688 reduced PO-induced increases in myofibroblasts, and scar tissue collagen content based upon immunofluorescence staining for α-smooth muscle actin and vimentin, scanning electron microscopy, and picrosirius red staining. ALY688 reduced PO-induced myocardial expression of 14 pro-inflammatory genes and circulating IL-12, IL-15, IL-17, and MIP-3α levels. Targeted metabolomics revealed that ALY688 increased myocardial fatty acid oxidation, with increased mobilization of cardiac triacylglycerols and a decrease in sphingomyelin, fatty acids and lysophospholipids. In conclusion, the adiponectin analogue ALY688 is cardioprotective in a preclinical animal model of heart failure and cardiac remodeling, with beneficial metabolic, anti-fibrotic, anti-hypertrophic and anti-inflammatory properties leading to improved cardiac function.

P53 Regulates the Extent of Fibroblast Proliferation and Fibrosis in Left Ventricle Pressure Overload.

Cardiomyopathy is characterized by the pathological accumulation of resident cardiac fibroblasts that deposit ECM (extracellular matrix) and generate a fibrotic scar. However, the mechanisms that control the timing and extent of cardiac fibroblast proliferation and ECM production are not known, hampering the development of antifibrotic strategies to prevent heart failure. We used the Tcf21 (transcription factor 21)MerCreMer mouse line for fibroblast-specific lineage tracing and p53 (tumor protein p53) gene deletion. We characterized cardiac physiology and used single-cell RNA-sequencing and in vitro studies to investigate the p53-dependent mechanisms regulating cardiac fibroblast cell cycle and fibrosis in left ventricular pressure overload induced by transaortic constriction. Cardiac fibroblast proliferation occurs primarily between days 7 and 14 following transaortic constriction in mice, correlating with alterations in p53-dependent gene expression. p53 deletion in fibroblasts led to a striking accumulation of Tcf21-lineage cardiac fibroblasts within the normal proliferative window and precipitated a robust fibrotic response to left ventricular pressure overload. However, excessive interstitial and perivascular fibrosis does not develop until after cardiac fibroblasts exit the cell cycle. Single-cell RNA sequencing revealed p53 null fibroblasts unexpectedly express lower levels of genes encoding important ECM proteins while they exhibit an inappropriately proliferative phenotype. in vitro studies establish a role for p53 in suppressing the proliferative fibroblast phenotype, which facilitates the expression and secretion of ECM proteins. Importantly, Cdkn2a (cyclin-dependent kinase inhibitor 2a) expression and the p16Ink4a-retinoblastoma cell cycle control pathway is induced in p53 null cardiac fibroblasts, which may eventually contribute to cell cycle exit and fulminant scar formation. This study reveals a mechanism regulating cardiac fibroblast accumulation and ECM secretion, orchestrated in part by p53-dependent cell cycle control that governs the timing and extent of fibrosis in left ventricular pressure overload.

The PERInatal MYocardial Remodeling (PERIMYR) cohort study protocol: A prospective study of cardiac remodeling and “recovery” in pregnancy as a model to understand the impact of comorbidities in cardiac remodeling and reverse remodeling

IntroductionHeart failure (HF) is among the leading causes of morbidity and mortality worldwide. Several conditions trigger left ventricular chronic pressure or volume overload, hypertrophy, systolic and diastolic dysfunction, leading to cardiac remodeling and a rapid progression toward HF. Therapeutic interventions elicit reverse remodeling (RR), a highly variable myocardial response that ranges from none to total ventricular structural/functional recovery. However, HF patients present several comorbidities and medications that mask a comprehensive molecular knowledge of RR and hinder the identification of potential biomarkers of its progression or prognosis. Therefore, instead of using this heterogeneous population or even animal models to understand myocardial remodeling, we propose studying pregnancy-induced cardiovascular remodeling and postpartum-induced RR. ObjectivesTo assess cardiovascular functional and structural adaptations during pregnancy and in postpartum, characterizing the associated molecular changes; as well as to explore the impact of hypertension, obesity and diabetes on these processes. MethodsWe will perform echocardiography and assess endothelial function and arterial stiffness (EndoPAT® and pulse wave velocity, respectively) and assess potential markers of remodeling and RR using plasma and urine samples from pregnant women. To translate to a HF context, we will determine the impact of risk factors (hypertension, obesity and diabetes) by studying subgroups of pregnant women with these comorbidities. ResultsNot applicable. ConclusionWe are convinced that understanding the impact of these comorbidities in such a homogeneous population, such as pregnant women, provides a valuable model to unveil the most relevant pathologic and often masked signaling pathways underlying cardiac remodeling and incomplete RR in a heterogeneous population, such as HF patients. Moreover, we expect to identify potential novel biomarkers of RR progression/prognosis more easily.

Phospholamban pentamerization increases sensitivity and dynamic range of cardiac relaxation.

A key event in the regulation of cardiac contraction and relaxation is the phosphorylation of phospholamban (PLN) that relieves the inhibition of the sarco/endoplasmic Ca2+-ATPase SERCA2a. PLN exists in an equilibrium between monomers and pentamers. While only monomers can inhibit SERCA2a by direct interaction, the functional role of pentamers is still unclear. This study investigates the functional consequences of PLN pentamerization. We generated transgenic mouse models expressing either a PLN mutant that cannot form pentamers (TgAFA-PLN) or wildtype PLN (TgPLN) in a PLN-deficient background. TgAFA-PLN hearts demonstrated 3-fold stronger phosphorylation of monomeric PLN, accelerated Ca2+ cycling of cardiomyocytes and enhanced contraction and relaxation of sarcomeres and whole hearts in vivo. All of these effects were observed under baseline conditions and abrogated upon inhibition of protein kinase A (PKA). Mechanistically, far western kinase assays revealed that PLN pentamers are phosphorylated by PKA directly and independent of any subunit exchange for free monomers. In vitro-phosphorylation of synthetic PLN demonstrated that pentamers even provide a preferred PKA substrate and compete with monomers for the kinase, thereby reducing monomer phosphorylation and maximizing SERCA2a inhibition. However, β-adrenergic stimulation induced strong PLN monomer phosphorylation in TgPLN hearts and sharp acceleration of cardiomyocyte Ca2+ cycling and hemodynamic values that now were indistinguishable from TgAFA-PLN and PLN-KO hearts. The pathophysiological relevance of PLN pentamerization was evaluated using transverse aortic constriction (TAC) to induce left ventricular pressure overload. Compared to TgPLN, TgAFA-PLN mice demonstrated reduced survival after TAC, impaired cardiac hemodynamics, failure to respond to adrenergic stimulation, higher heart weight, and increased myocardial fibrosis. The findings show that PLN pentamerization greatly impacts on SERCA2a activity as it mediates the full range of PLN effects from maximum inhibition to full release of SERCA2a. function. This regulation is important for myocardial adaptation to sustained pressure overload. Pentamerization of PLN adds to the regulation of cardiac contractile function and facilitates myocardial transition to an energy saving mode during resting phases. Thus, PLN pentamers would protect cardiomyocytes from energetic deficits, and they improve stress adaptation of the heart as shown for sustained pressure overload in this study. Strategies that target PLN pentamerization promise therapeutic potential in the treatment of myocardial maladaptation to stress as well as cardiac pathologies associated with altered monomer-to-pentamer ratios, e.g., cardiomyopathies due to PLN mutations, certain types of heart failure, and aged hearts.

PS-BPB09-5: BROWN ADIPOSE TISSUE DYSFUNCTION PROMOTES METABOLIC DISORDER IN A FAILING HEART.

Objective: Low body temperature predicts poor clinical outcomes in patients with heart failure, however, underlying mechanisms and pathological implications are largely unknown. Brown adipose tissue (BAT) was initially characterized as a heat generating organ, and studies suggest it has crucial roles for maintaining systemic metabolic health. The purpose of this study was to determine whether alteration of BAT function contributes to development of heart failure. Design and method: We generated two murine heart failure models, thoracic aortic constriction (TAC) and myocardial infarction (MI). We analyzed cardiac function, thermogenic response, and pathological findings in the hearts of these mice. We also performed comprehensive metabolomic analyses in the heart, BAT, and plasma samples from sham- and TAC-operated mice. Results: We found murine models with TAC or MI induced BAT dysfunction, and this led to a significant reduction in body temperature. Chronic activation of adrenergic signaling induced apoptosis in brown adipocytes, and surgical denervation of sympathetic nerves innervating BAT improved thermogenic response and cardiac systolic dysfunction. Gain of BAT function model, generated with BAT implantation into peritoneal cavity, improved thermogenesis and ameliorated cardiac dysfunction in TAC. In contrast, systolic function was reduced in genetically BAT dysfunctional model, and this associated with poor survival rate in this model. Metabolomic analyses showed that BAT dysfunction led to an increase of choline and its downstream metabolite, trimethylamine N-oxide (TMAO) that promoted metabolic dysfunction in the failing heart. TMAO administration resulted in a significant reduction in phosphocreatine or ATP level in cardiac tissues, and this was mediated by the suppression of complex IV activity in mitochondria. Genetic or pharmacological inhibition of TMAO production ameliorated cardiac dysfunction during left ventricular pressure overload. Dilated cardiomyopathy patients had lower body temperature, and this associated with an increase in circulating choline and TMAO level. Conclusions: Alteration of BAT function contributes to the development of heart failure via increased TMAO. Our findings suggest that maintenance of BAT homeostasis and reducing TMAO production could be potential next-generation therapies for heart failure.

Cardiomyocyte PAI-1 influences the cardiac transcriptome and limits the extent of cardiac fibrosis in response to left ventricular pressure overload

Plasminogen activator inhibitor-1 (PAI-1) is a specific and rapid-acting inhibitor of endogenous plasminogen activators (uPA and tPA). The global PAI-1 knockout mice (PAI-1KO) develop age-dependent cardiac-selective fibrosis, and young global PAI-1KO mice exhibit augmented susceptibility to developing cardiac fibrosis in response to hypertension. Here, we tested the hypothesis that cardiomyocyte PAI-1 is necessary to provide cardioprotective effects in a left ventricular pressure overload-induced murine model of cardiac hypertrophy and fibrosis using cardiomyocyte-specific PAI-1 knockout (cmPAI-1KO) mice. The results revealed that cmPAI-1KO mice display significantly worse cardiac fibrosis than controls. To investigate the molecular mechanisms responsible for these effects, genome-wide cardiac transcriptome analysis was performed. Loss of cardiomyocyte PAI-1 led to differential expression of 978 genes compared to controls in response to left ventricular pressure overload. Pathway enrichment analysis identified the inflammatory response, cell substrate adhesion, regulation of cytokine production, leukocyte migration, extracellular matrix organization, and cytokine-mediated signaling pathways as being significantly upregulated in cmPAI-1KO hearts. Conversely, specific epigenetic repressors, cation transmembrane transport, muscle system processes, and nitric oxide signaling were significantly downregulated in cmPAI-1KO hearts compared to control hearts in response to left ventricular pressure overload. Collectively, the present study provides strong evidence of the impact of cardiomyocyte PAI-1 in regulation of the transcriptome network involved in the cardiac stress response. In response to stress, the deregulatory impact of cardiomyocyte PAI-1 loss on the cardiac transcriptome may be the underlying cause of cardiac-selective accelerated fibrogenesis in global PAI-1-deficient mice.

150 ECHO-DERIVED LEFT VENTRICULAR MECHANO-ENERGETIC EFFICACY CHARACTERIZES HYPERTENSIVE PATIENTS WITH IMPAIRED PET-DERIVED MYOCARDIAL BLOOD FLOW

Abstract Background Chronic left ventricular (LV) pressure overload determines both morphological and functional alterations in the heart and in the vascular system with occurrence of LV hypertrophy, coronary rarefaction and metabolic impairment, predisposing to heart failure. We aim at investigating early cardiac involvement in hypertensive disease by both Positron emission tomography (PET) and echo assessment and possible associations between alterations of PET-derived myocardial blood flow (MBF) and echocardiographic parameters of LV performance including mechano-energetic efficiency indexed for myocardial mass (MEEi), in a population of symptomatic hypertensive patients without flow-limiting epicardial coronary artery disease (CAD). Methods The study population included 78 symptomatic hypertensive patients without flow-limiting epicardial CAD. All patients underwent standard echocardiographic assessment, including evaluation of LV MEEi, and PET assessment with evaluation of MBF and MBF/mass ratio at rest and after stress and myocardial flow reserve (MFR). Results The study population included 67% males, 55% with dyslipidaemia, 42% with smoking habits and 21% obese. Prevalence of LV hypertrophy was of 43%. Among parameters of LV systolic performance, hyperaemic MBF/mass ratio resulted significantly correlated with LV MEEi (r=0.54, p<0.0001), midwall fractional shortening (r=0.38, p=0.001) but not with LVEF (r=0.10, p=0.47). Similarly, resting MBF/mass ratio resulted to have statistically significant correlations with LV MEEi (r=0.51, p<0.0001), midwall fractional shortening (r=0.29, p=0.01) but not with LVEF (r=0.11, p=0.39). LV MEEi reached the highest correlation coefficient with both resting and stress MBF/mass ratio. On the other hand, the correlation between MEEi and MFR did not reach statistical significance (r=0.11, p=0.33). In a multiple linear regression analysis, after adjusting for sex, systolic blood pressure, prevalence of LV hypertrophy and therapy with diuretics, the association between LV MEEi and hyperaemic MBF/mass ratio remained significant (beta coefficient =0.40, p=0.007). In a subsequent multivariate model, adjusting for the same confounders, by replacing hyperaemic MBF/mass ratio with resting MBF/mass ratio, LV MEEi and resting MBF/mass ratio continued to be significantly associated (beta coefficient =0.32, p=0.015). Conclusions In a population of hypertensive patients without flow-limiting epicardial CAD, an early myocardial impairment possibly related to coronary rarefaction and inadequate angiogenesis contributing to the altered myocardial metabolic demand and efficacy is detectable by both PET and echo-derived LV MEEi. Indeed, an independent association between LV MEEi and both MBF/mass ratio at rest and after stress exists, LV MEEi having the advantage over PET of being easily derived from standard echocardiography and not needing radiation exposure.

Abstract 15684: Prognostic Value of Cardiac Damage Staging in Adults With Repaired Coarctation of Aorta

Background: Chronic left ventricular (LV) pressure overload is common in adults with repaired coarctation of aorta (COA). However, there is no validated systematic approach for assessing cardiac remodeling and damage in this population. The purpose of this study was to evaluate the role of cardiac damage staging scheme (validated for calcific aortic stenosis) for prognostication in adults with repaired COA. Methods: Patients were classified using a modified cardiac damage scheme: stage 0 (no cardiac damage), stage 1 (LV damage), stage 2 (left atrial damage), stage 3 (pulmonary vascular/tricuspid valve damage), and stage 4 (right ventricular damage). Results: Of 795 patients (age 36±16 years), 270 (34%) had stage 0, 198 (25%) had stage 1, 225 (28%) had stage 2, 37 (5%) had stage 3, and 65 (8%) had stage 4 cardiac damage. The 795 patients were followed for 7.3 (2.8-9.6) years, and 94 (12%) died, of which 75 (9%) were cardiovascular deaths. Cardiac damage stage was independently associated with all-cause mortality (adjusted HR 1.31, 95% CI 1.22-1.40, per unit increase in stage), and cardiovascular mortality (adjusted HR 1.42, 95% CI 1.28-1.55, per unit increase in stage). The addition of the cardiac damage stage to the base model (clinical and echocardiographic variables) provided significant incremental improvement in the prediction of 5-year risk of all-cause mortality over the base model (net reclassification index 0.39, p<0.001). Hypertension was associated with cardiac damage and mortality. Conclusions: The cardiac damage scheme can be used for risk stratification, and potentially guide therapy in the COA population.

Abstract 15337: Chronic Oral Finerenone Treatment Does Not Improve Left Ventricular Diastolic Compliance in Swine With Repetitive Pressure Overload-Induced HFpEF

Introduction: The non-steroidal mineralocorticoid receptor antagonist finerenone has emerged as a potential treatment for heart failure with preserved ejection fraction (HFpEF) based, in part, on initial evidence of its anti-fibrotic properties. However, it is unclear whether chronic oral finerenone therapy can reverse established cardiac fibrosis. Accordingly, we tested the efficacy of chronic oral finerenone in a porcine model of HFpEF characterized by interstitial fibrosis and reduced left ventricular (LV) diastolic compliance in the absence of co-morbidities or anatomic LV hypertrophy. Methods: Swine (n=12) were subjected to daily (1 hr) episodes of repetitive LV pressure overload (RPO) for 2 weeks using phenylephrine (24 mg/hr) to transiently elevate LVEDP to ~30 mm Hg. After 2 weeks, RPO was discontinued and animals were followed for an additional 4 weeks, during which a subset received oral finerenone (20 mg/day; n=6). LV end-diastolic volume (EDV) and pressure (EDP) were measured at normal and elevated preload to assess LV compliance (ΔLVEDV/ΔLVEDP) and post-mortem picrosirius red staining was performed to quantify interstitial fibrosis vs. normal controls (n=8). Results: Four-weeks after cessation of RPO, untreated animals exhibited a significant increase in interstitial fibrosis vs. normal controls that was attenuated in finerenone-treated animals ( Figure A ). Despite this regression of interstitial collagen, a persistent reduction in LV diastolic compliance was observed after finerenone treatment (1.18 ± 0.33 mL/mmHg vs. 2.11 ± 0.22 mL/mmHg in normal controls; p=0.04) that was comparable to that of untreated animals after RPO (0.97 ± 0.22 mL/mmHg; p=0.61; Figure B ). Conclusion: Four weeks of chronic oral finerenone treatment does not restore LV diastolic compliance in swine with RPO-induced HFpEF despite regression of interstitial collagen content, suggesting that other factors may contribute to diastolic stiffening in this model.