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Background The Spontaneously Hypertensive Rat (SHR) Colony was established in 1963 and is the most commonly used rodent model for studying heart failure (HF). Ideally, animal models should recapitulate the clinical disease as closely as possible. Any drift in a genetic model may create a new model that no longer adequately represents the human pathology. Further, instability overtime may lead to conflicting data between laboratories and/or irreproducible results. While systolic blood pressure (SBP) is closely monitored during inbreeding, the sequelae of HF (e.g., cardiac hypertrophy) are not. Thus, the object of this review was to investigate whether the hypertension-induced sequelae of HF in the SHR have remained stable after decades of inbreeding. Methods A systematic review was performed to evaluate indices of cardiovascular health in the SHR over the past 60 years. For post hoc statistical analyses, studies were separated into 2 cohorts: Initial (mid to late 1900s) and Current (early 2000s to present) Colony SHRs. Wistar-Kyoto rats (WKY) were used as controls. Results SBP was consistent between Initial and Current Colony SHRs. However, Current Colony SHRs presented with increased concentric hypertrophy (i.e., elevated heart weight and posterior wall thickness) while cardiac output remained consistent. Since these changes were not observed in the WKY controls, cardiac-derived changes in Current Colony SHRs were unlikely due to differences in environmental conditions. Conclusions Together, these data firmly establish a cardiac-based phenotypic shift in the SHR model and provide important insights into the beneficial function of concentric hypertrophy in hypertension-induced HF.

Maintenance of the kidney filtration barrier requires coordinated interactions between podocytes and the underlying glomerular basement membrane (GBM). GBM ligands bind podocyte integrins, which triggers actin-based signaling events critical for adhesion. Nck1/2 adaptors have emerged as essential regulators of podocyte cytoskeletal dynamics. However, the precise signaling mechanisms mediated by Nck1/2 adaptors in podocytes remain to be fully elucidated.We generated podocytes deficient in Nck1 and Nck2 and used transcriptomic approaches to profile expression differences. Proteomic techniques identified specific binding partners for Nck1 and Nck2 in podocytes. We used cultured podocytes and mice deficient in Nck1 and/or Nck2, along with podocyte injury models, to comprehensively verify our findings.Compound loss of Nck1/2 altered expression of genes involved in actin binding, cell adhesion, and extracellular matrix composition. Accordingly, Nck1/2-deficient podocytes showed defects in actin organization and cell adhesionThese findings reveal distinct, yet complementary, roles for Nck proteins in regulating podocyte adhesion, controlling GBM composition, and sustaining filtration barrier integrity.

Consumption of highly colored fruits and vegetables rich in anthocyanins has been associated with numerous health benefits. Purple carrots (PC) and purple potatoes (PP) have higher anthocyanin concentrations and higher biological activities compared with less pigmented cultivars. We hypothesized that substitution of the majority of carbohydrate in a high fat diet with PP or PC, for 8 weeks, would improve insulin resistance and hypertension, major components of metabolic syndrome, compared with orange carrots (OC), white potatoes (WP) or a control, high fat, sucrose-rich diet (HFD) in obese Zucker rats. After 8 weeks of feeding, intraperitoneal glucose tolerance test, intraperitoneal insulin tolerance test (ipITT), and invasive hemodynamic tests were performed. The PP group had better glucose tolerance compared with the WP and the HFD groups and higher insulin sensitivity as measured by the ipITT and homeostatic model assessment of insulin resistance (P = .018) compared with the HFD without having any effect on blood pressure. The PC reduced left ventricular pressure compared with both the HFD (P = .01) and the OC (P = .049) groups and reduced systolic and diastolic blood pressures compared with the HFD group (P = .01 and

Traditionally, the evaluation of cardiac function has focused on systolic function; however, there is a growing appreciation for the contribution of diastolic function to overall cardiac health. Given the emerging interest in evaluating diastolic function in all models of heart failure, there is a need for sensitivity, accuracy, and precision in the hemodynamic assessment of diastolic function. Hemodynamics measure cardiac pressures in vivo, offering a direct assessment of diastolic function. In this review, we summarize the underlying principles of diastolic function, dividing diastole into two phases: 1) relaxation and 2) filling. We identify parameters used to comprehensively evaluate diastolic function by hemodynamics, clarify how each parameter is obtained, and consider the advantages and limitations associated with each measure. We provide a summary of the sensitivity of each diastolic parameter to loading conditions. Furthermore, we discuss differences that can occur in the accuracy of diastolic and systolic indices when generated by automated software compared with custom software analysis and the magnitude each parameter is influenced during inspiration with healthy breathing and a mild breathing load, commonly expected in heart failure. Finally, we identify key variables to control (e.g., body temperature, anesthetic, sampling rate) when collecting hemodynamic data. This review provides fundamental knowledge for users to succeed in troubleshooting and guidelines for evaluating diastolic function by hemodynamics in experimental models of heart failure.Listen to this article’s corresponding podcast at https://ajpheart.podbean.com/e/assessment-of-diastolic-function/ .

Dyspnea and reduced exercise capacity, caused, in part, by respiratory muscle dysfunction, are common symptoms in patients with heart failure (HF). However, the etiology of diaphragmatic dysfunction has not been identified. To investigate the effects of HF on diaphragmatic function, models of HF were surgically induced in CD-1 mice by transverse aortic constriction (TAC) and acute myocardial infarction (AMI), respectively. Assessment of myocardial function, isolated diaphragmatic strip function, myofilament force-pCa relationship, and phosphorylation status of myofilament proteins was performed at either 2 or 18 wk postsurgery. Echocardiography and invasive hemodynamics revealed development of HF by 18 wk postsurgery in both models. In vitro diaphragmatic force production was preserved in all groups while morphometric analysis revealed diaphragmatic atrophy and fibrosis in 18 wk TAC and AMI groups. Isometric force-pCa measurements of myofilament preparations revealed reduced Ca2+sensitivity of force generation and force generation at half-maximum and maximum Ca2+activation in 18 wk TAC. The rate of force redevelopment ( ktr) was reduced in all HF groups at high levels of Ca2+activation. Finally, there were significant changes in the myofilament phosphorylation status of the 18 wk TAC group. This includes a decrease in the phosphorylation of troponin T, desmin, myosin light chain (MLC) 1, and MLC 2 as well as a shift in myosin isoforms. These results indicate that there are multiple changes in diaphragmatic myofilament function, which are specific to the type and stage of HF and occur before overt impairment of in vitro force production.

A growing proportion of heart failure (HF) patients present with impairments in both ventricles. Experimental pressure-overload (i.e., transverse aortic constriction, TAC) induces left ventricle (LV) hypertrophy and failure, as well as right ventricle (RV) dysfunction. However, little is known about the coordinated progression of biventricular dysfunction that occurs in TAC. Here we investigated the time course of systolic and diastolic function in both the LV and RV concurrently to improve our understanding of the chronology of events in TAC. Hemodynamic, histological, and morphometric assessments were obtained from the LV and RV at 2, 4, 9, and 18 weeks post-surgery. Results: Systolic pressures peaked in both ventricles at 4 weeks, thereafter steadily declining in the LV, while remaining elevated in the RV. The LV and RV followed different structural and functional timelines, suggesting the patterns in one ventricle are independent from the opposing ventricle. RV hypertrophy/fibrosis and pulmonary arterial remodeling confirmed a progressive right-sided pathology. We further identified both compensation and decompensation in the LV with persistent concentric hypertrophy in both phases. Finally, diastolic impairments in both ventricles manifested as an intricate progression of multiple parameters that were not in agreement until overt systolic failure was evident. Conclusion: We establish pulmonary hypertension was secondary to LV dysfunction, confirming TAC is a model of type II pulmonary hypertension. This study also challenges some common assumptions in experimental HF (e.g., the relationship between fibrosis and filling pressure) while addressing a knowledge gap with respect to temporality of RV remodeling in pressure-overload.

Diaphragmatic weakness is a feature of heart failure (HF) associated with dyspnea and exertional fatigue. Most studies have focused on advanced stages of HF, leaving the cause unresolved. The long-standing theory is that pulmonary edema imposes a mechanical stress, resulting in diaphragmatic remodeling, but stable HF patients rarely exhibit pulmonary edema. We investigated how diaphragmatic weakness develops in two mouse models of pressure overload-induced HF. As in HF patients, both models had increased eupneic respiratory pressures and ventilatory drive. Despite the absence of pulmonary edema, diaphragmatic strength progressively declined during pressure overload; this decline correlated with a reduction in diaphragm cross-sectional area and preceded evidence of muscle weakness. We uncovered a functional codependence between angiotensin II and β-adrenergic (β-ADR) signaling, which increased ventilatory drive. Chronic overdrive was associated with increased PERK (double-stranded RNA-activated protein kinase R-like ER kinase) expression and phosphorylation of EIF2α (eukaryotic translation initiation factor 2α), which inhibits protein synthesis. Inhibition of β-ADR signaling after application of pressure overload normalized diaphragm strength, Perk expression, EIF2α phosphorylation, and diaphragmatic cross-sectional area. Only drugs that were able to penetrate the blood-brain barrier were effective in treating ventilatory overdrive and preventing diaphragmatic atrophy. These data provide insight into why similar drugs have different benefits on mortality and symptomatology, despite comparable cardiovascular effects.

Noonan syndrome (NS) is caused by mutations in RAS/ERK pathway genes, and is characterized by craniofacial, growth, cognitive and cardiac defects. NS patients with kinase-activatingRAF1alleles typically develop pathological left ventricular hypertrophy (LVH), which is reproduced inRaf1L613V/+knock-in mice. Here, using inducibleRaf1L613Vexpression, we show that LVH results from the interplay of cardiac cell types. CardiomyocyteRaf1L613Venhances Ca2+sensitivity and cardiac contractility without causing hypertrophy.Raf1L613Vexpression in cardiomyocytes or activated fibroblasts exacerbates pressure overload-evoked fibrosis. Endothelial/endocardial (EC)Raf1L613Vcauses cardiac hypertrophy without affecting contractility. Co-culture and neutralizing antibody experiments reveal a cytokine (TNF/IL6) hierarchy inRaf1L613V-expressingECs that drives cardiomyocyte hypertrophyin vitro. Furthermore, post-natal TNF inhibition normalizes the increased wall thickness and cardiomyocyte hypertrophyin vivo. We conclude that NS cardiomyopathy involves cardiomyocytes, ECs, and fibroblasts, TNF/IL6 signaling components represent potential therapeutic targets, and abnormal EC signaling might contribute to other forms of LVH.

Hypertrophic cardiomyopathy (HCM) has multiple etiologies, including hypertension, cardiac valve disease or genetic defects. Most inherited HCM results from defects in sarcomere proteins, but ~25% are caused by aberrant cardiac signal transduction genes. RASopathies are developmental disorders with multiple variably penetrant features, including HCM, which are caused by mutations in genes encoding RAS/extracellular signal-regulated kinase (ERK) pathway components. The most common RASopathy, Noonan Syndrome (NS), results from gain-of-function alleles in PTPN11, KRAS, SHOC2, SOS1/2, RAF1 and RIT1. Activating mutations in RAF1 are strongly (~95%) associated with HCM. Global knock-in mice harboring the NS allele Raf1L613V recapitulate the features of NS-associated HCM, including ventricular chamber dilatation, enhanced cardiac contractility, and exacerbation of pressure-overload induced fibrosis. Here, using inducible Raf1L613V knock-in mice and lineage-specific Cre lines, we show that RAF1 mutant-associated HCM is caused by a complex interplay of multiple cardiac cell types. Surprisingly, cardiomyocyte-specific Raf1L613V expression caused minimal hypertrophy, yet markedly increased cardiac contractility. By contrast, endocardial/cardiac endothelial (EC)-specific Raf1L613V expression promoted cardiomyocyte hypertrophy without affecting contractility. In direct or Transwell co-cultures, Raf1L613V-expressing ECs increased the size of normal cardiomyocytes. Cytokine arrays revealed increased IL6 secretion from isolated Raf1L613V-expressing ECs, and JAK-STAT, PI3K, and MEK/ERK activation were enhanced in EC-Raf1L613V hearts. Blocking IL6 action with neutralizing anti-IL6 antibodies reversed cardiomyocyte hypertrophy in EC/cardiomyocyte co-cultures. Finally, Raf1L613V expression in cardiomyocytes or cardiac fibroblasts, but not in ECs, exacerbated fibrosis upon pressure-overload. Taken together, our data indicate that NS HCM requires complex, cell-autonomous and -non-autonomous interactions between cardiomyocytes, ECs, and fibroblasts. Furthermore, we identify the IL6 pathway as a potential therapeutic target for RASopathy-associated HCM.

Background Echocardiography is a valuable noninvasive technique to estimate cardiac output (CO) from the left ventricle (LV) not only in clinical practice but also in small-animal experiments. CO is used to grade cardiac function and is especially important when investigating cardiac injury (e.g., myocardial infarction [MI]). Critically, MI deforms the LV, invalidating the assumptions fundamental to calculating of cardiac volumes directly from the LV. Thus, the purpose of this study was to determine if Doppler-derived blood flow through the pulmonary trunk (pulmonary flow [PF]) was an improved method over conventional LV–dependent echocardiography to accurately determine CO after MI. Methods Variations in CO were induced either by transverse aortic constriction or MI. Echocardiography was performed in healthy ( n = 27), transverse aortic constriction ( n = 25), and MI ( n = 41) mice. CO calculated from PF (pulsed-wave Doppler) was internally compared with CO calculated from left ventricular images using M-mode (Teichholz formula) and the single-plane ellipsoid two-dimensional (2D) formula and externally compared with the gold standard, flow probe CO. Results In healthy mice, all three echocardiographic methods (M-mode, 2D, and PF) correlated well with flow probe–derived CO. In MI mice, only PF CO values correlated well with flow probe values. Bland-Altman analysis confirmed that PF was improved over M-mode and 2D echocardiography. Inter- and intrauser variability of PF CO was reduced, and both inter- and intraclass correlation coefficients were improved compared with either M-mode or 2D CO calculations. Conclusions PF CO calculated from pulsed-wave Doppler through the pulmonary trunk was an improved method of estimating CO over LV–dependent formulas after MI.

Exercise intolerance, characterized by dyspnea and early onset of exertional fatigue, is a chief complaint among patients with heart failure (HF). Limb muscle dysfunction is a known contributor to ...